Douglas-fir trees are impacted by many types of insects that feed on the bark or living tissue. Depending on the signs and symptoms, the tree may be impacted by a different insect or issue. A common bark beetle that feeds on Douglas-fir is the Douglas-fir bark beetle. This is a native insect that typically feeds on trees greater than 10" in diameter at breast height. What you are seeing looks like signs of the beetle, with exit holes and pitch on the main trunk of the tree. Adult beetles lay eggs in the bark, then the larvae feed on the living tissue (phloem) between the bark and the sapwood. Once the beetles mature, they exit the tree, leaving behind the small holes. Live, green trees often have pitch, or sap, on the outer bark during a beetle infestation. 

While bark beetles are a natural part of the ecosystem, their presence usually indicates that your trees are stressed from other factors. Douglas-fir beetles are typically secondary pests, meaning that they infest stressed trees or trees already declining. For example, the extreme heat events of 2020 have significantly impacted tree health in western Oregon, and warmer temperatures and more frequent droughts stress trees year to year, making them more prone to threats like bark beetle. Outbreaks of the beetle can occur after storm events when there are many downed trees in an area. One recommendation is to remove large-diameter downed trees after storms before the first April to reduce risk of outbreak.

You can learn more about how to identify signs and symptoms of the Douglas-fir beetle here, as well as management guidelines: https://www.oregon.gov/odf/Documents/forestbenefits/Douglas-fir-beetle.pdf.

If you have other, healthy trees nearby, you can consider using MCH pheromone as a preventative measure. You can buy pouches relatively cheaply online. MCH pheromone is a natural compound that deters beetles from infesting dead and live trees and is proven to be effective for individual trees and small forest areas (up to 24 acres). However, it is a deterrent and is not guaranteed to protect trees. It is best applied before beetles emerge and fly in April. Note that MCH is a pesticide, so read and follow the product label before use. You can find more information about using MCH here:

https://www.oregon.gov/odf/Documents/forestbenefits/mch-for-douglas-fir-beetle.pdf

https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5157034.pdf

You can also refer to to other AskExtension questions here.